This invention relates to ultrasonic transducer arrays and a method for their fabrication, and especially to arrays with impedance matching layers on the front surface for use in medical ultrasound examinations and water tank applications.
The general technique for high sensitivity ultrasonic transducers has been described. The crucial feature is that with two quarter wave matching transformers there is greatly improved energy transfer from the high impedance sources, such as piezoelectric ceramic, to water or to a human body. On known arrays both matching layers are continuous.
Currently manufactured transducer arrays commonly have a solid wear plate covering the surface of the array which is made of an epoxy-like material. This plastic acts as an inefficient matching layer and also refracts acoustic energy away from the ceramic except for incidence angles small (typically less than .+-.20.degree.) compared to those required by a wide angle sector scanner.
The transducer array for a phased array sector scan imaging system must have a broad field of view, high sensitivity, and short impulse duration, and the prior art does not satisfy all these requirements.